1. Field of the Invention
The present invention involves a mixing and reducing machine with an upward-conveying mixing spiral that rotates around a vertical rotational axle.
2. Description of the Related Art
A machine of this type with two interlocking flat helical springs is known, for example, from the German Patent No. 23 34 789 and German Patent No. 26 38 112. In these previously known mixing and reducing machines, two spirals that mesh with each other are provided. They are mounted on rotating axles that are set apart from each other at a distance to the side. For these rotating axles, between two and four rotary transmission leadthroughs must be provided, depending on the construction, through the cover or the bottom of the container in which the spirals are provided. This container also has an expensive double construction with an essentially figure-eight shaped cross-section. This structural form does indeed make possible an intensive mixing, in which relatively small portions of the mixed good are stirred by the one and then by the other spiral, but is very complicated in its design.
The purpose of the invention presented here is thus to provide a corresponding mixing and reducing machine in which a simpler construction is possible, in which, in particular, the container construction is less complicated, and with which, however, in spite of that, a sufficient mixing quality is achieved.
This purpose is achieved according to the invention in that after the first mixing spiral mentioned, a second mixing spiral is arranged in the axial direction, whereby a transition zone extends between the mixing spirals in the axial direction.
The invention has the advantage that only one rotating axle must be present. This axle can be set in bearings in a correspondingly simple manner with only one or at maximum two rotating embodiments on the container provided. Moreover, the invention has the advantage that although only one rotating axle is present in it, a sufficient intermixing is achieved. This is especially possible in a simple container in the form of a cylinder that can be manufactured in an uncomplicated manner.
In the previously known mixing machines with only one rotating axle, only one mixing spiral is customarily present, and it is continuous. This makes it so that the mixed product is conveyed continuously upwards in the area of the mixing spiral that is radially to the outside relative to the rotating axle, and thenxe2x80x94customarily in the area of the centrally arranged rotating axlexe2x80x94drops to the bottom again because of the force of gravity. This does not lead, in the end, to a fast and intensive mixing.
In the embodiment form now proposed according to the invention with two mixing spirals that are connected one after the other in the axial direction and are separated by a transition zone, it is achieved that zones having different axial conveying quantities are connected one after the other, which promotes the intensive intermixing. This is especially the case when the transition zone is free of mixing spirals and the mixed product is thus slowed down at the beginning of the transition zone and is accelerated again at the end of the transition zone through the subsequently connected second mixing spiral. The shearing forces acting as a result in the mixed product lead to a surprisingly intensive mixing.
It should also be mentioned here that for larger systems, several mixing spirals arranged axially behind each other can also be present, each separated by transition zones. For the sake of simplicity, this will not be dealt with separately in the following.
Fundamentally, the two mixing spirals connected axially one after the other, both of which fundamentally convey in the same axial direction upwards, also have different axial conveyed quantities, whereby in the axial direction, an additional shearing gradient occurs, which amplifies the intermixing.
This different axial conveyed quantity can either be achieved in that the two mixing spirals have different helix angles or, however, in that the two mixing spirals have different spiral blade widths.
It is also possible to connect single-flighted or multiple-flighted spirals after each other.
As an additional possibility, to increase the shearing effect in the area of the transition zone, in order to thus increase the mixing effect, it can be provided that the two mixing spirals that are connected one after the other have different rotational speeds or have different rotational directions.
In order to increase the effectiveness of mixing with the spirals, it has proven to be especially favorable if at least one of the spirals provided is interrupted in the circumferential direction and is comprised of mixing blades that are connected after each other in the circumferential direction. Through this type of interruption of the mixing spiral, the mixed product is mixed in an especially intensive manner, since it is moved in especially small volumes by the blades, and comes to rest again. Moreover, each mixing blade can be equipped with a different conveying angle both in the axial and in the radial direction, whereby an additionally improved mixing effect can be obtained.
A further improvement of the intermixing is achieved when at least individual mixing blades have, on their ends that are trailing in the rotating direction, a lifting edge that is bent upwards, through which a brief impulse directed upwards is imparted to a mixed good portion lifted by the mixing blades, before this mixed product portion begins to drop again due to the force of gravity, whereby it is then picked up again by a trailing mixing blade and further intermixed accordingly.
In a special embodiment form of this type of mixing spiral comprised of mixing blades, two mixing blades at a time are arranged essentially above each other are connected to each other by an essentially vertically running blade carrier that is set in the rotational direction. With this blade carrier, on which if necessary, even more than two blades arranged above each other can be mounted, the mixed product can be accelerated or slowed down in the radial direction.
This is possibly further amplified because the mixing blades (and/or the blade carrier that connects them) are attached through carrier arms to a central shaft, the front surface of which is chamfered increasingly, at least in sections, radially to the outside. This also increases a mixing effect in the radial direction of the otherwise only vertically operating mixer.
In order to further intensify the mixing effect, at least individual mixing blades can additionally mesh on their outer side with catchment elements located on the container wall. Through the shearing that occurs in the area of the catchment elements, the mixing effect is greatly increased.
In the process, the catchment elements can involve both closed ring elements as well as toothed ring elements that are mounted on the container wall. These ring elements can in the process either be arranged only in segments over the circumference of the container or, instead over its entire circumference.
An additional improvement of the mixing effect is obtained when on one end of the mixing blades a shearing head is arranged essentially aligned with the vertical rotating axle, with which the mixed good that is dropping centrally around the rotating axle is again sheared. Also, a desired radial or axial conveyance of the mixed good can be influenced here. Advantageously, this shearing head acts together with a counter head, which has a different rotational speed and/or direction.